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Valluru, Srividya. „Steady state thermal stress analyses of two-dimensional and three-dimensional solid oxide fuel cells“. Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3887.
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Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains ix, 138 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 90-94).
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Němec, Petr. „Měnič pro BLDC motor“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442792.
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The goal of this Master thesis is to design a power convertor for BLDC motor 48V/2kW. Emphasis is placed on the small dimensions of the final printed circuit board. Therefore, power SMD transistors STL135N8F7AG are used in small packages PowerFlat 5x6. To reduce area of the PCB, electrolytic capacitors are mounted on a separate board, which is located above the main PCB. Small high-capacity 22F/100V ceramic capacitors are used in the DC-LINK as well. They are located as close as possible to the power SMD tranzistors. Control logic will be provided by microprocesor STM32G474RE. High resolution timer HRTIM1 is used. The first part of this thesis is devoted to the brief description of BLDC motor construction and driving. Next parts are focused on the design itself.
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Ferroni, Paolo Ph D. Massachusetts Institute of Technology. „Steady state thermal hydraulic analysis of hydride fueled BWRs“. Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41263.
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Includes bibliographical references (p. 205-208).Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.
(cont.) Since the results obtained in the main body of the analysis account only for thermal-hydraulic constraints, an estimate of the power reduction due to the application of neutronic constraints is also performed. This investigation, focused only on the "New Core" cases, is coupled with an increase of the thickness of the gap separating adjacent bundles from 2 to 5 mm. Under these more conservative conditions, the power gain percentages are lower, ranging between 24% and 43% (depending on the discharge burnup considered acceptable) for the upper pressure drop limit, and between 17% and 32% for the lower pressure drop limit.
(cont.) The benefits of the latter approach are evident since the space occupied by the bypass channel for cruciform control rod insertion becomes available for new fuel and a higher power can be achieved. The core power is constrained by applying thermal-hydraulic limits that, if exceeded, may induce failure mechanisms. These limits concern Minimum Critical Power Ratio (MCPR), core pressure drop, fuel average and centerline temperature, cladding outer temperature and flow-induced vibrations. To limit thermal-hydraulic instability phenomena, core power and coolant flow are constrained by fixing their ratio to a constant value. In particular, each BWR/5 core has been analyzed twice, each time with a different pressure drop limit: a lower limit corresponding to the pressure drop of the reference core and an upper limit 50% larger. It has been demonstrated that, in absence of neutronic constraints and with the maximum allowed pressure drop fixed at the upper limit, the implementation of the hydride fuel yields power gain percentages, with respect to oxide cores chosen as reference, of the order of 23% when its implementation is performed following the "Backfit" approach and even higher (50-70%) when greater design freedom is allowed in the core design, i.e. in the "New Core" approach. Should the maximum allowed pressure drop be fixed at the lower limit, the power gain percentage of the "Backfit" approach would decrease to 17%, while that of the "New Core" approach would remain unchanged, i.e. 50-70%.
This thesis contributes to the Hydride Fuel Project, a collaborative effort between UC Berkeley and MIT aimed at investigating the potential benefits of hydride fuel use in Light Water Reactors (LWRs). Considerable work has already been accomplished on hydride fueled Pressurized Water Reactor (PWR) cores. This thesis extends the techniques used in the PWR analysis to examine the potential power benefits resulting from the implementation of the hydride fuel in Boiling Water Reactors (BWRs). This work is the first step towards the achievement of a complete understanding of the economic implications that may derive from the use of this new fuel in BWR applications. It is a whole core steady-state analysis aimed at comparing the power performance of hydride fueled BWR cores with those of typical oxide-fueled cores, when only thermal-hydraulic constraints are applied. The integration of these results with those deriving from a transient analysis and separate neutronic and fuel performance studies will provide the data required to build a complete economic model, able to identify geometries offering the lowest cost of electricity and thus to provide a fair basis for comparing the performance of hydride and oxide fuels. Core design is accomplished for two types of reactors: one smaller, a BWR/5, which is representative of existing reactors, and one larger, the ESBWR, which represents the future generation of BWRs. For both, the core design is accomplished in two ways: a "Backfit" approach, in which the ex-bundle core structure is identical to that of the two reference oxide cores, and a "New Core" approach, in which the control rods are inserted into the bundles in the form of control fingers and the gap between adjacent bundles is fixed optimistically at 2 mm.
by Paolo Ferroni.
S.M.
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Huning, Alexander. „A steady state thermal hydraulic analysis method for prismatic gas reactors“. Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52196.
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A new methodology for the accurate and efficient determination of steady state thermal hydraulic parameters for prismatic high temperature gas reactors is developed. Two conceptual reactor designs under investigation by the nuclear industry include the General Atomics GT-MHR and the Department of Energy MHTGR-350. Both reactors use the same hexagonal prismatic block, TRISO fuel compact, and circular coolant channel array design.
Steady state temperature, pressure, and mass flow distributions are determined for the base reference designs and also for a range of values of the important parameters. Core temperature distributions are obtained with reduced computational cost over more highly detailed computational fluid dynamics codes by using efficient, correlations and first-principles-based approaches for the relevant thermal fluid and thermal transport phenomena. Full core 3-D heat conduction calculations are performed at the individual fuel pin and lattice assembly block levels. The fuel compact is treated as a homogeneous medium with heat generation. A simplified 1-D fluid model is developed to predict convective heat removal rates from solid core nodes. Downstream fluid properties are determined by performing a channel energy balance down the axial node length. Channel exit pressures are then compared and inlet mass flows are adjusted until a uniform outlet pressure is reached. Bypass gaps between assembly blocks as well as coolant channels are modeled. Finite volume discretization of energy, and momentum conservation equations are then formed and explicitly integrated in time. Iterations are performed until all local core temperatures stabilize and global convective heat removal matches heat generation.
Several important observations were made based on the steady state analyses for the MHTGR and GT-MHR. Slight temperature variation in the radial direction was observed for uniform radial powers. Bottom-peaked axial power distributions had slightly higher peak temperatures but lower core average temperatures compared to top and center-peaked power distributions. The same trend appeared for large bypass gap sizes cases compared to smaller gap widths. For all cases, peak temperatures were below expected normal operational limits for TRISO fuels. Bypass gap flow for a 3 mm gap width was predicted to be between 10 and 11% for both reactor designs. Single assembly hydrodynamic and temperature results compared favorably with those available in the literature for similar prismatic HTGR thermal hydraulic, computational fluid dynamics analyses.
The method developed here enables detailed local and core wide thermal analysis with minimal computational effort, enabling advanced coupled analyses of high temperature reactors with thermal feedback. The steady state numerical scheme also offers a potential for select transient scenario modeling and a wide variety of design optimization studies.
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Wiser, Travis Sloan. „Steady state heat transfer characterization of a liquid metal thermal switch“. Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Summer2005/T%5FWiser%5F062205.pdf.
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Hioe, Yunior. „Mold thermal design and quasi steady state cycle time analysis in injection molding“. Connect to resource, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141840509.
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Marshallsay, P. G. „A methodology for modelling the steady-state thermal performance of air conditioning systems /“. Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phm3692.pdf.
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Madrid, Lozano Francesc. „Thermal Conductivity and Specific Heat Measurements for Power Electronics Packaging Materials. Effective Thermal Conductivity Steady State and Transient Thermal Parameter Identification Methods“. Doctoral thesis, Universitat Autònoma de Barcelona, 2005. http://hdl.handle.net/10803/5348.
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Derakhshan, Jamal Jon. „Innovations Involving Balanced Steady State Free Precession MRI“. Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1247256364.
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Thesis (Ph.D.)--Case Western Reserve University, 2009Title from PDF (viewed on 19 August 2009) Department of Biomedical Engineering Includes abstract Includes bibliographical references Available online via the OhioLINK ETD Center
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Lindén, Ronja, und Henrik Samuelsson. „Thermal analysis and design improvement of light module fixture“. Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Maskinteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-30485.
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Introduction One of the products made by SAAB Avionics Systems in Jönköping was in need of a better cooling solution. The product, a Head-Up Display, holds a LED that was overheating when run at desired input power. The purpose of this thesis was to identify the design weaknesses in the current solution regarding heat dissipation and produce new design proposals that fulfill the requirements. The parts analyzed consist of a LED light source, adjustment plates and a heat sink. The adjustment plates and heat sink where covered in a surface treatment. Theoretical framework A simulation of a finite element model was set up of the current solution in order to identify the influence of the different parts and their thermal properties. The simulation was set up as a steady state thermal model. The FEM and steady state equations used during this are mentioned and shortly explained. The state of modern research was found in order to find new innovative ways of solving the heat problem. Method In order to understand the current solution, experimentswere carried out. Interviews were used in order to get the correct information easily. A literature study was preformed to understand the different theories. Reverse engineering was applied to get a detailed understanding of the functionality both mechanically and thermally. Brainstorming was used to generate new solutions, which was followed by a feasibility evaluation and Pugh’s method to sort out the best concepts. Implementation and Result Based on the simulations it can be concluded that some of the developed solutions pass the requirements and can be implemented right away. Some need some more work in order to fully pass the demands. Conclusions The thermal flow was greatly affected by the properties of the aluminum in the adjustment plates and heat sink, though there was not much room for thickness reduction. However, the oxide layer and the surface roughness also had a great impact on the high junction temperature. The requirements where therefore met when adjustment plates and interfaces were removed, to lower the amount of oxide and air between the LED and the heat sink. But the oxide layers needed to be thinner and the surface roughness needed to be reduced in order to meet requirements. If the oxide layers need to stay at current thickness or the surface roughness cannot be changed, the heat sink needs to be redesigned. The recommended concepts were smaller than the current solution. If this space is utilized with a bigger heat sink, the goals can be met with greater ease. There is also room for improvement when it comes to heat sink heat spreader pattern. Discussion The discussion covers what knowledge which was needed to write this thesis and how different problems that occurred along its path were solved. Sustainability in different ways was also discussed.
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Zhang, Mingyang. „Detailed Heat Transfer Measurements of Various Rib Turbulator Shapes at Very High Reynolds Numbers Using Steady-state Liquid Crystal Thermography“. Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/81859.
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In order to protect gas turbine blades from hot gases exiting the combustor, several intricate external and internal cooling concepts are employed. High pressure stage gas turbine blades feature serpentine passages where rib turbulators are installed to enhance heat transfer between the relatively colder air bled off from the compressor and the hot internal walls. Most of the prior studies have been restricted to Reynolds number of 90000 and several studies have been carried out to determine geometrically optimized parameters for achieving high levels of heat transfer in this range of Reynolds number. However, for land-based power generation gas turbines, the Reynolds numbers are significantly high and vary between 105 and 106. Present study is targeted towards these high Reynolds numbers where traditional rib turbulator shapes and prescribed optimum geometrical parameters have been investigated experimentally. A steady-state liquid crystal thermography technique is employed for measurement of detailed heat transfer coefficient. Five different rib configurations, viz., 45 deg., V-shaped, inverse V-shaped, W-shaped and M-shaped have been investigated for Reynolds numbers ranging from 150,000 to 400,000. The ribs were installed on two opposite walls of a straight duct with aspect ratio of unity. For very high Reynolds numbers, the heat transfer enhancement levels for different rib shapes varied between 1.3 and 1.7 and the thermal hydraulic performance was found to be less than unity.Master of Science
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Allen, Diana M. „Steady-state and transient hydrologic, thermal and chemical modelling of a faulted carbonate aquifer used for aquifer thermal energy storage, Carleton University, Ottawa, Canada“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22158.pdf.
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Allen, Diana M. (Diana Margaret) Carleton University Dissertation Earth Sciences. „Steady-state and transient hydrologic, thermal and chemical modelling of a faulted carbonate aquifer used for Aquifer Thermal Energy Storage, Carleton University, Ottawa, Canada“. Ottawa, 1996.
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Ritz, Guillaume Henri [Verfasser]. „Performance of tungsten-based materials and components under ITER and DEMO relevant steady-state thermal loads / Guillaume Henri Ritz“. Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018203524/34.
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Gossard, Justin. „Numerical Simulation of the Steady-State, Thermal-Hydraulic Performance of Microchannel and Minichannel Evaporators with Headers and Louvered Fins“. Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1323289158.
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Plank, Jack R. „Nuclear Thermal Propulsion Cool-Down Phase Optimization Through Quasi-Steady Computational Analysis, and the Effect of Auxiliary Heat Removal Systems“. The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618934609976051.
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Hedström, Sofia. „Thermal energy recovery of low grade waste heat in hydrogenation process“. Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-32335.
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The waste heat recovery technologies have become very relevant since many industrial plants continuously reject large amounts of thermal energy during normal operation which contributes to the increase of the production costs and also impacts the environment. The simulation programs used in industrial engineering enable development and optimization of the operational processes in a cost-effective way. The company Chematur Engineering AB, which supplies chemical plants in many different fields of use on a worldwide basis, was interested in the investigation of the possibilities for effective waste heat recovery from the hydrogenation of dinitrotoluene, which is a sub-process in the toluene diisocyanate manufacture plant. The project objective was to implement waste heat recovery by application of the Organic Rankine Cycle and the Absorption Refrigeration Cycle technologies. Modeling and design of the Organic Rankine Cycle and the Absorption Refrigeration Cycle systems was performed by using Aspen Plus® simulation software where the waste heat carrier was represented by hot water, coming from the internal cooling system in the hydrogenation process. Among the working fluids investigated were ammonia, butane, isobutane, propane, R-123, R-134a, R-227ea, R-245fa, and ammonia-water and LiBr-water working pairs. The simulations have been performed for different plant capacities with different temperatures of the hydrogenation process. The results show that the application of the Organic Rankine Cycle technology is the most feasible solution where the use of ammonia, R-123, R-245fa and butane as the working fluids is beneficial with regards to power production and pay-off time, while R-245fa and butane are the most sustainable choices considering the environment.
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Fox, Brandon S. „In-Pile Thermal Conductivity Measurement Methods for Nuclear Fuels“. DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/660.
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Measuring nuclear fuel thermal conductivity in-pile can provide much needed data for understanding fuel performance during irradiation and yield thermophysical property data needed for simulation codes and fuel databases. The objective of this research is to develop and compare two in-pile thermal conductivity methods in a laboratory setting using surrogate fuel materials.
A steady-state radial heat flow method was investigated to understand its viability as an in-pile steady-state thermal conductivity technique. By using Joule heating to simulate volumetric heat generation within a surrogate fuel rod, thermal conductivity was measured with two thermocouples at different radial positions within the rod. Examinations were completed on two batches of surrogate materials over the temperature range of 500 to 700 °C. The selected surrogate rod was fabricated from the only material identified to possess the required thermal conductivity and electrical resistivity required for the selected laboratory approach. Evaluations estimated a measurement uncertainty of 12% and values were within 33% of values obtained using laboratory material property measurement systems for this surrogate material. Results indicate that the selected surrogate rod material limited the ability to assess this approach at higher temperatures in a laboratory setting.
A transient needle probe method adapted from American Standard Test Method standards was also used to measure temperature-dependent thermal conductivity of surrogate fuel rod materials for temperatures ranging from room temperature to 400 °C. The needle probe has a heating element and a temperature sensor contained in a metal sheath, and it is inserted into the surrogate fuel rod whose thermal conductivity is to be measured. The thermal conductivity is calculated from the power applied to the heating element, and the temperature rise detected in the sample. Needle probes were designed and fabricated using materials recommended for in-pile application. Scoping room-temperature values obtained using the needle probe method were within acceptable accuracies defined by the ASTM needle probe reference standard. Temperature-dependent values were within 2% of values for the well-characterized ASTM recommended reference material, fused silica. A measurement uncertainty under 6% was calculated for the needle probe method.
As a result of this study, the needle probe method was selected for additional testing at the Idaho National Laboratory for anticipated testing in Materials Test Reactors. This would result in the first-ever transient in-pile thermal conductivity sensor.
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Slabbert, Rohan. „Thermal–hydraulics simulation of a benchmark case for a typical Materials Test Reactor using Flownex / Slabbert R“. Thesis, North-West University, 2011. http://hdl.handle.net/10394/7575.
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The purpose of this study was to serve as a starting point in gaining understanding and experience of simulating a typical Pool Type Research Reactor with the thermal hydraulic software code Flownex®. During the study the following evaluations of Flownex® were done:
* Assessment of the simplifying assumptions and possible shortcomings built into the software.
* Definition of the applicable modelling methodology and further simplifying assumptions that have to be made by the user.
* Evaluation of the accuracy and compatibility with the Pool Type Research Reactor.
* Comparing the results of this study with similar studies found in the open literature.
For the study the IAEA MTR 10 MW benchmark reactor (IAEA, 1992a) was used. A steady state simulation using Flownex® was done on a single fuel assembly, and this was compared with a model that was developed using the software package EES (Engineering Equation Solver). The results have shown good agreement between the different packages. After this verification, a steady state simulation of the entire core was done to obtain the characteristics of the reactor operating under normal condition. Finally, transient simulations were done on various LOFAs (Loss of Flow Accidents). The results of the various LOFAs were compared with studies that were previously done on the IAEA MTR 10 MW reactor.Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2012.
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Tagliati, Stella. „Membrane-based nanocalorimetry for low temperature studies with high resolution and absolute accuracy“. Doctoral thesis, Stockholms universitet, Fysikum, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-64523.
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A differential, membrane-based nanocalorimeter has been designed and constructed for thermal studies of mesoscopic samples at low temperatures. The calorimeter is intended for sample masses from mg to sub-μg and a broad temperature range from above room temperature down to the sub-K region. It allows concurrent use of ac steady state and relaxation methods. Effort was spent to achieve good absolute accuracy to enable investigations of the electronic contribution to the heat capacity of superconductors. The calorimeter consists of a pair of cells, each of which is a stack of heaters and thermometer in the center of a silicon nitride membrane, in total giving a background heat capacity less than 100 nJ/K at 300 K, decreasing to 10 pJ/K at 1 K. The device has several distinctive features: i) The resistive thermometer, made of a GeAu alloy, displays a high sensitivity, dlnR/dlnT ≈ −1 over the entire temperature range. ii) The sample is placed in direct contact with the thermometer, which is allowed to self-heat. The thermometer can thus be operated at high dc current to increase the resolution. iii) Data are acquired with a set of eight synchronized lock-in amplifiers measuring dc, 1st and 2nd harmonic signals of heaters and thermometer. iv) Absolute accuracy is achieved via a novel variable-frequency fixed-phase technique in which the measurement frequency is automatically adjusted during ac-calorimetry measurements to account for the temperature variation of the sample specific heat and the device thermal conductance. The properties of the empty cell and the effect of the thermal link between sample and cell were analytically studied. Practical expressions for describing the frequency dependence of heat capacity, thermal conductance, and temperature oscillation amplitude of the system were formulated. Comparisons with measurements and numerical simulations show excellent agreement. Calibration procedures are simple, but care should be taken to minimize thermal radiation effects. The experimental setup is operated with self-regulation of heater powers and thermometer bias, including compensation to zero the differential dc signal. As a result its high resolution and compact format, the calorimeter is well suited for studies of phase transitions and phase diagrams as well as electronic specific heat. The performance of the device is demonstrated by a study of the superconducting state of a small lead crystal.En differentiell, membran-baserad nanocalorimeter har designats och tillverkats för termiska studier av mesoskopiska prover vid låg temperatur. Kalorimetern är avsedd för provmassor från mg till sub-μg och ett brett temperaturområde från över rumstemperatur till under 1 K. Den tillåter samtidig användning av både ac steady state och relaxations-metod. Fokus har lagts på att uppnå en god absolut noggrannhet för att möjliggöra studier av det elektroniska bidraget till värmekapaciteten hos supraledare. Kalorimetern består av två celler, var och en uppbyggd som en stack med värmeelement och termometer i mitten av ett kiselnitrid-membran, med en total bakgrundsvärmekapacitet på mindre än 100 nJ/K vid 300 K, minskande till 10 pJ/K vid 1 K. Kalorimetern har flera särdrag: i) Den resistiva termometern, gjord av en GeAu legering, visar en hög känslighet, dlnR/dlnT ≈ −1 över hela temperaturområdet. ii) Provet placeras i direkt kontakt med termometern, som tillåts att självvärma. Termometern kan alltså användas vid hög dc ström för att öka upplösningen. iii) Mätningarna genomförs med en uppsättning av åtta synkroniserade lock-in förstärkare, som mäter dc, grundfrekvens och 1:a övertonen hos värme-element och termometer. iv) Absolut noggrannhet uppnås genom en ny variabel-frekvens konstant-fas teknik där mätfrekvensen justeras automatiskt under ac-kalorimetrimätningar för att kompensera temperaturberoendet hos provets specifika värmekapacitet och kalorimetercellens värmeledningsförmåga. Egenskaperna hos den tomma cellen och inverkan av den termiska länken mellan prov och cell studerades analytiskt. Praktiska uttryck för att beskriva frekvens beroendet hos systemets värmekapacitet, värmeledningsförmåga, och temperaturoscillationer har formulerats. Jämförelser mellan mätningar och numeriska simuleringar visar mycket bra överensstämmelse. Kalibreringsförfarandet är enkelt, men försiktighet bör vidtas för att minimera värmestrålningseffekter. Experimentuppställningen drivs med självreglering av värmare och termometer, inklusive kompensation för att nollställa den differentiella dc signalen. Som en följd av dess höga upplösning och kompakta format är kalorimetern väl lämpad för studier av fasövergångar och fasdiagram såväl som det elektroniska specifika värmet. Kalorimeterns prestanda demonstreras genom en studie av det supraledande tillståndet hos en liten blykristall.
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Accepted.
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Poinas, Philippe. „Contribution a la modelisation numerique et a l'etude experimentale du champ thermique stationnaire 3d au sein d'un microcomposant electronique“. Nantes, 1987. http://www.theses.fr/1987NANT2007.
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Etude de la fiabilite d'un composant electronique par une simulation thermique tridimensionnelle en situation reelle. Elle est basee sur une modelisation numerique. La concordance entre les temperatures theoriques et experimentales se revele tres satisfaisante
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Cristea, Alex Florian. „Analysis of thermal effects in circumferential groove journal bearings with reference to the divergent zone“. Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2313/document.
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Ce travail porte sur l'étude des effets thermiques dans un palier hydrodynamique, alimentée par une rainure circonférentielle (CGJB) sous charge statique, en tenant compte des phénomènes de rupture de film dans la zone divergente. La recherche expérimentale a été réalisée à l'Université de Poitiers ; elle a permis une détermination minutieuse des champs de pression et de température sur la portée située à l’avant d’un CGJB et dans la section médiane de sa rainure. Ces mesures sous un régime stationnaire sont originales par rapport celles existantes, quel que le type de palier, de par le grand nombre de points de mesure, 180 pour la pression et 144 pour la température, l'instrumentation de haute précision, la large plage de conditions d'exploitation (pression spécifique variant de 0,125 à 2 MPa et vitesse linéaire de l’arbre allant de 5,25 à 21 m/s). Des études du régime transitoire de démarrage au régime stationnaire établi ont été effectuées pour de faibles charges. Des expériences effectuées à l'Université "Politehnica" de Bucarest ont montré une bonne corrélation entre la perte de portance, anti-portance et la rupture du film sur un patin Rayleigh (RSP), ce qui est essentiel pour l'évaluation des phénomènes de rupture dans les paliers. Quelques modèles théoriques ont été utilisés pour évaluer les risques de serrage au démarrage qui est une instabilité thermoélastique catastrophique. Les principaux résultats sont l’obtention d’une base fiable de données expérimentales permettant le développement des modèles théoriques avancés et l’infirmation d’une répartition de pression constante dans la zone divergente et de pression et température constantes dans la rainure d'alimeThe main objective of the thesis is to study the thermal effects in steadily loaded circumferential groove journal bearings (CGJBs), including cavitation phenomena occurring in the divergent zone of such bearings. Experimental research conducted at University of Poitiers – Institut Pprime – France enabled a thorough determination of film pressure and temperature fields for the front land of a CGJB plus its mid-groove section, and several performance parameters. Measurements of film pressure and temperature fields under steady-state regime surpassed existing works, regardless of journal bearing design, through: sheer number of land measurement locations, 180 for pressure and for 144 temperature; high precision state of art instrumentation; broad range of operating conditions, 0.125 … 2 MPa specific bearing pressure and 5.25 … 21 m/s shaft speeds. Transient start-up to steady-statestabilization regimes have been investigated at low loads. Experiments at University "Politehnica" of Bucharest – Romania showed a correlation between the downforce thrust and film rupture for a Rayleigh step pin (RSP), important in evaluating divergent zone cavitation phenomena. Theoretical research consisted in developing simple models for evaluating CGJBs performance in steady-state and transient start-up regimes. Several theoretical models were employed for assessing start-up seizure, catastrophic transient thermoelastic instability and damage risk. The major result is a reliable experimental data collection that: enables development of advanced theoretical models; disprove flat film pressure distributions in divergent zones, and constant pressure and temperature in the bearing supply groov
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Kongo, Konde Ange. „Modélisation du roulement d'un pneumatique d'avion“. Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10009.
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Ce travail de thèse présente la démarche utilisée pour construire un modèle éléments finis en statique ou en dynamique d'un pneumatique d'avion gros porteur prenant en compte la géométrie, la structure matérielle complexe, les différents matériaux et leurs propriétés ainsi que les interactions entre le pneumatique et le sol (contact, frottement et couplage thermomécanique). Des essais ont été effectués afin d'identifier les paramètres géométriques et matériaux.Ces simulations utilisant une approche Lagrangienne et une approche mixte Eulérienne/Lagrangienne ont été réalisées sur le modèle proposé. La seconde approche qui réduit considérablement le temps de calcul a été validée pour simuler le roulement en dérapage du pneumatique. Le modèle permet ainsi d'estimer le torseur des efforts dans le contact pneumatique /sol. Nous montrons l'influence des paramètres de chargement (charge verticale, pression de gonflage et vitesse de roulage) et de l'angle de dérapage sur le moment d'autoalignement (MZ) et sur le potentiel d'adhérence (µY) correspondant au rapport entre l'effort latéral et l'effort vertical dû au poids de l'avion. Nous présentons aussi une étude de sensibilité aux paramètres géométriques et matériels.Des essais de Coulomb et de diffusion thermique ont permis d'identifier la loi d'évolution du coefficient de frottement en fonction de la température (béton, asphalte) et l'évolution de la température dans l'épaisseur du pneumatique. Ceci a permis de prendre en compte les effets thermiques dans le modèle et de proposer un modèle de couplage thermomécanique qui met en évidence la décroissance de µY et la chute rapide de MZ vers des valeurs négatives au-delà d'un angle de dérapage critique βmax variant avec les conditions de chargement du pneumatique. Ces variations sont observées expérimentalementThis PhD Thesis presents the approach adopted for the setting of numerical model based on Finite Element Method for jumbo-jet tire. The model takes into account the real geometry, the complex material structure, the various materials and their properties as well as the interactions between the tire and the ground (contact, friction and thermal-mechanical coupling due to friction). Tests are performed in order to identify geometrical and material parameters.Static and dynamic simulations using a Lagragian approach and an Eulerian/ Lagrangian mixed approach were performed on this proposed model. This second approach which significantly reduces the computational cost time was validated for cornering tire simulation. The model allows thereby to estimate the forces in the tire/ ground contact patch. We show the influency of loading parameters (vertical load, inflating pressure and rolling velocity) and of the slip angle on the self aligning torque (MZ) and on the lateral friction coefficient (µY) corresponding on the ratio between lateral force and vertical load due to the aircraft weight. We also present a sensitivity study on geometrical and material parameters.Coulomb's and thermal diffusion tests were performed in order to identify the friction coefficient law as function of temperature (on concrete and asphalte surfaces) and the temperature evolution in the aircraft tire thickness. These tests allowed to take into account thermal effects in the model and to propose a thermal-mechanical coupling model which emphasized the decreasing of µY and the rapid vanishing of MZ towards zero beyond a critical slip angle βmax varying with the tire loading conditions. These variations were observed experimentally
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Devellioglu, Yucel. „Electronic Packaging And Environmental Test And Analysis Of An Emi Shielded Electronic Unit For Naval Platform“. Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609459/index.pdf.
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The scope of this thesis is the design and verification of an electronic packaging of a device which is a subunit of a network system that is designed for combat communication in sheltering ship. According to the project requirements this device is subjected to some environmental and electromagnetic interference tests. This thesis includes design and manufacturing steps as well as vibration, shock and thermal analyses. Electromagnetic interference is examined through the design procedure and total shielding effectiveness of the device is calculated after the applications of some electromagnetic interference precautions which are given in details.
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El, Khomssi Mohammed. „Étude des équations paraboliques et elliptiques gérant l'état thermique d'un supraconducteur“. Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL107N.
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L'état thermique d'un supraconducteur unidimensionnel est géré par une équation parabolique semi-linéaire ; le terme source représente ici la compétition entre la puissance volumique dissipée dans le conducteur par effet joule et celle qui est absorbée par le bain cryogénique de température Tb dont le rôle est de maintenir l'installation en dessous de sa température critique Tc. Après une perturbation thermique accidentelle (pendant laquelle seules les extrémités du conducteur peuvent être strictement contrôlées par le bain), la température du conducteur évolue de façon transitoire vers l'une des trois solutions stationnaires éventuellement possibles, parmi lesquelles T = Tb est la seule souhaitable. Ce mémoire propose: un certain nombre de critères suffisants, portant sur des paramètres physiques de l'installation, pour que T = Tb soit la seule solution stationnaire possible du problème ; une explicitation numérique d'un critère optimal (parce que nécessaire et suffisant) proposé dans une thèse antérieure mais peu exploitable sous sa forme théorique ; un calcul numérique des deux solutions stationnaires autres que Tb ; lorsque aucun des critères proposés ne peut être satisfait ; quelques informations sur l'évolution de la température après une perturbation thermique ; plusieurs généralisations de l'étude: situation tridimensionnelle, coefficient dépendant de la température, forme du terme source
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Pakiru, Swapna. „Effect of Step Change in Growth Speed During Directional Solidification on Array Morphology of Al-7 wt% Si Alloy“. Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1323970093.
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Hodot, Romain. „Modeling and test of loop heat pipes for civil and military avionic applications“. Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0132.
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Dans les années à venir, l’industrie de l’aéronautique doit améliorer le contrôle thermique des composants et modules hautement intégrés. Les approches de refroidissement standard, utilisant l’air forcé ne sont plus utilisables. Il est donc nécessaire de développer de nouvelles technologies capables d’offrir des solutions compatibles avec ces nouvelles problématiques. Une revue bibliographique approfondie est présentée pour montrer les solutions existantes pour l’avionique. Les systèmes à changement de phase, tels que les boucles diphasiques capillaires (LHPs), sont très attractifs puisqu’ils peuvent être utilisés pour transporter la chaleur vers une grande surface d’un radiateur qui dissipera la chaleur vers le milieu ambiant. Une première famille de LHP, conçue et réalisée par la compagnie Atherm, et remplie avec du méthanol, est décrite. Deux autres familles de LHP sont également présentées. La première a été réalisée par la société ATHERM et a un condenseur et des lignes de transports modifiés, afin d’être intégrée sur une carte électronique existante. La deuxième famille, a été conçue et réalisée par l’Institut of Thermal Physics (ITP), sur la base de spécifications similaires. Un banc d’essai expérimental est conçu et réalisé pour tester ces systèmes. Les effets de la charge en fluide, baïonnette, et mèche secondaire, sont observés. Des tests d’orientation et d’accélération sont réalisés sur des LHPs intégrées dans un rack aéronautique. Même une certaine sensibilité aux orientations et accélérations est observée, les LHPs fonctionnement toujours jusqu’à l’accélération maximale testée de 6 G. Un modèle stationnaire d’une boucle diphasique basé sur une approche à plusieurs échelles est développé. Plusieurs niveaux de complexité et de précision peuvent être sélectionnés pour le modèle des composants individuels de la boucle, allant du modèle nodal au modèle 3D. Le modèle est validé avec les données expérimentales. Un bon accord entre les simulations numériques et les résultats expérimentaux est obtenu. Les résultats numériques montrent que la charge de fluide dans le réservoir affecte le comportement thermique de la LHP en modifiant la répartition des flux de chaleurs. Des gradients de température importants sont observés dans la plaque du condenseur, et un nouveau tracé de la ligne condenseur est proposé. Plusieurs modifications de l’évaporateur sont analysées. La diminution la plus importante de la résistance thermique de l’évaporateur est obtenue par une bonne disposition des rainures axiales de la mèche, associée à une semelle optimisée, ou à des rainures radialesIn the coming years, the avionics industry will have to improve the thermal control of both existing and emerging highly integrated electronic components and modules. The standard cooling approaches using forced air are no longer applicable. It is necessary to develop new technologies being able to offer solutions compatible with those new problematic. An extensive literature review is presented to show the existing cooling solutions for avionics. Two-phase passive systems, such as LHPs are very attractive as they may be used as heat spreader, associated with a classical heat sink to dissipate the heat. A first family of LHP, designed and manufactured by the ATHERM Company and filled with methanol as the working fluid is described. Two other LHP families are also presented. The first one was manufactured by ATHERM and has modified condenser and transport line shapes, in order to be integrated into an existing electronic card. The second one was manufactured and designed by the Institute of Thermal Physics, on the same specification basis. An experimental setup is designed and built to test these LHPs. The effects of fluid fill charge, bayonet and secondary wick are observed. Orientation and acceleration tests are conducted on LHPs integrated within an avionic rack. Even if the LHPs exhibited sensitivity to orientation and acceleration, no failure of the LHP was observed up to the maximum applied acceleration (6 G). A steady state model of LHP based on a multi-level approach is developed. Various levels of complexity and precision can be selected for the model of the individual component, going from the nodal to the 3D model. The model is validated with experimental data from the laboratory tests. A good agreement is achieved between the experimental and the numerical data. The numerical results show that the fluid fill charge within the reservoir affects the thermal behavior of the LHP, by modifying the heat flux distribution. High temperature gradients are highlighted in the condenser plate and a redesign of its shape is proposed. Various modifications of the evaporator design are considered. The most important decrease of the evaporator thermal resistance is brought by a good disposition of the axial vapor grooves associated with an optimized saddle shape or radial vapor grooves
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Chou, Kuo, und 洪國洲. „Study of steady state thermal lensing effect in organic solutions“. Thesis, 2005. http://ndltd.ncl.edu.tw/handle/65098501728487379310.
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碩士國立中正大學
物理所
93
This thesis investigates the thermal nonlinear refraction and nonlinear transmission properties of an ethanolic solution of chloroaluminum phthalocyanine in the continuous wave regime. Particularly, we focus on the dependence of the irradiance as well as solvent and solute concentration to the thermal nonlinear refraction. Besides, we confirm the previous observed ambiguous transmittance decrease around the beam waist at high input irradiance. Using a lens of larger cross section to collect the transmitted laser pulse, we do not see this decrease again and thus believe the previous observed transmittance decreases arise from an experimental error. Our investigation indicates that the samples show saturable absorption and the thermal nonlinear refraction causes a negative lensing effect” which increases with the light irradiance, solute concentration and solvents.
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Chou, Hsin-Feng, und 周欣鋒. „Steady-state thermal stress analysis of a planar solid oxide fuel cell“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/41160372749716373596.
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碩士國立中央大學
機械工程研究所
95
Planar solid oxide fuel cell is composed of the interconnect, positive electrode-electrolyte-negative electrode (PEN), frame, glass-ceramic, and porous nickel. At steady-state operation, the temperature is high and the thermal stresses in planar SOFC are caused by the temperature gradients and mismatch of coefficient of thermal expansion (CTE) between all cell components. When the thermal stresses in a fuel cell are sufficiently high, gas leakage or failure may occur in the SOFC components. This will reduce the SOFC efficiency. A steady-state thermal stress analysis of SOFC is necessary for the design of SOFC. Commercial FEA code ANSYS is utilized to analyze the thermal stress distribution in planar SOFC under steady-state condition in this study. A 3-D model based on a developing planar SOFC design would be constructed in the current study to perform a thermal stress analysis for planar SOFC. We discuss the influence on thermal stress due to different constraint, different flow-path configurations, and the mismatch of CTE. Modeling results indicated that interconnect and frame might have plastic deformations under steady-state operation, but PEN and glass-ceramic were still in the range of strength security. Three different constraint at bottom interconnect of SOFC would not cause significant changes in the thermal stress distribution. The thermal stresses owing to co-flow are smaller than counter-flow, and co-flow is more safe for SOFC structure. Thermal stress distribution is fully influnced by temperature distribution when we ignore the mismatch of CTE.
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Woltman, Gregory. „STRUCTURAL AND STEADY-STATE THERMAL EXPERIMENTAL INVESTIGATIONS OF AN INSULATED SANDWICH PANEL“. Thesis, 2014. http://hdl.handle.net/1974/12178.
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Concrete-Insulation-Concrete Sandwich Panels with Glass Fibre Reinforced Polymer (GFRP) shear connectors can be a solution to increasing energy efficiency in building envelopes, while also providing many architectural, structural, and economic benefits for building designs. This study consists of extensive experimental investigation of the shear and thermal properties of a unique sandwich panel design, incorporating GFRP shear connectors and a concrete “stud” system. The goal of this study is to expand upon the knowledge of alternative connectors’ effect on structural and thermal properties of sandwich panels, and to develop a thermally, structurally, and economically efficient panel.
In the structural phase fifty 254x254x900 mm specimens representing segments of the precast sandwich wall, comprising two concrete wythes and a concrete stud surrounded by insulation foam, were tested in a double shear configuration. Three types of GFRP connectors produced from available sand-coated and threaded rods were tested and compared to conventional steel and polymeric connectors. GFRP connector diameters varied from 6 to 13 mm, and spacing varied from 80 to 300 mm. Both circular and rectangular cross-sections were examined, along with various end treatments to compare with simple straight embedment. The shear strength of GFRP connectors ranged from 60 to 112 MPa, significantly higher than polymeric connectors but lower than steel connectors. As the connectors bridged a small gap of insulation between the concrete wythe and stud, their shear strength was lower than manufacturer reported values due to the presence of some bending. Varying the size, spacing, cross-section shape or end treatment of connectors had insignificant effect on their strength. The connectors failed by longitudinal delamination then transverse shear, but did not pull out of the concrete wythe. Adhesion bond between concrete and insulation was significant and contributed about 28% of resistance, but was too variable for use in design.
In the thermal testing phase, ten 254x1550x2400 full-scale specimens were tested in a purpose-built hot box apparatus under steady-state conditions. GFRP connectors showed minimal thermal bridging regardless of cross-section area or spacing, while steel connectors demonstrated significant thermal bridging in recorded temperatures despite a smaller cross-section area, and were clearly visible in thermal imaging.Thesis (Master, Civil Engineering) -- Queen's University, 2014-05-06 13:32:38.896
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Chen, Jing-sian, und 陳憬憲. „Measurement of thermal resistance of LED package with infrared at Steady state“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/28706452906955256954.
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碩士國立中央大學
光電科學研究所
98
In this thesis, we used a high power infrared light source to emulate the heat source and built a novel system for thermal resistance measurement. In this system, a thermal camera is used to measure the temperature distribution. With the temperature distribution over the entire sample measured, we can obtain the thermal resistance of the test sample. All commercially available high power LED packages’ thermal resistances were measured based on the system that we constructed. The measurement results were compared with theoretical models which base on the finite element analysis method. Contact thermal resistance can also be estimated by comparing the experimental measurement results with the FEA simulation results. A brief discussion was provided about the contact thermal resistance contributed by different bonding methods which using different bonding material based on the analysis developed.
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Tang, Chung-Kau, und 田宗凱. „FEM Analysis of Steady-State Axisymmetric Extrusion Die Design－ The Study of Thermal Effect“. Thesis, 1996. http://ndltd.ncl.edu.tw/handle/45755403769865923525.
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碩士國立中山大學
機械工程研究所
84
In this dissertation, optimum stream-lined die length of axisymmetric steady-state extrusion processes will be investigated by adopting the penalty rigid-viscoplastic finite element method. In additional, we take the thermal coupled effect into consideration. The die profile is presented by a third-order polymonial , which simplifies the optimal process so that we can concentrate on the influence of temperature. In the thesis, the material AL1100(a) which exhibits the obvious change of material properties as its temperature differs is chosen to indicate the interesting results of va- riation of optimal die length when we analyze thermal coupled extrusion process. The primary factors including air convection coefficient, extrusion ratio, and friction factor will be discussed further.
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chao, hsin-lung, und 趙信隆. „steady state thermal stress analysis of three dimention smelting reduction vessel finite element model“. Thesis, 2000. http://ndltd.ncl.edu.tw/handle/50798383072284516228.
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碩士國立臺灣大學
應用力學研究所
88
Iron ore smelting reduction is one of new iron smelting processes. Because it emissions fewer pollution products, such as CO2, NOX, and SOX, etc. Besides it needs lower cost in raw material and economize the use of energy. The advantage of this process is that the constituents of carbon will all be transfer to carbon dioxide. The utility rate of coal can reach 100% in the theory. So all the advanced country of iron and steel industry are actively participate in exploiting the whole new iron smelting process. In order to adapt to the different region that bear to different substance and state. Foreign countries are starting to study the design of used of compound lining material. Our research use the finite element analysis software ABAQUS to create a three dimension iron ore smelting vessel model. We try to carry out the simulating and calculating of finite element method. So that we can observe the thermal stress distribute under the steady state temperature field of the iron ore smelting vessel model. The research followed a proper sequence to contribute the three dimensional iron ore smelting vessel model. After got the simulating result, we try to discuss the origin of the thermal stress distribution. And analyze the effect of the structure and material constant. Depend to the simulating result, we wish to estimate the real thermal stress condition of iron ore smelting vessel and offer safety improved suggestion.
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Chang, Chin-Hsiang, und 張錦祥. „The Study of a Simplified Hot Plate Method for a Steady-State Thermal Conductivity Measurement“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/86121300396261593721.
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博士長庚大學
機械工程研究所
95
In order to better understand the accuracy of a newly developed simplified hot plate method in measuring steady-state thermal conductivity, a numerical model for simulating the measurement is devised and verified by experimental results to perform the accuracy analysis. The ratios of the thermal conductivity derived from the temperature distribution solutions to that given in the numerical model are obtained and shown. They can be used to correct the systematic error of measurement introduced by the one-dimensional approximation in real applications. Furthermore, the measurement uncertainty due to power control, misalignment of the temperature sensors, and the limitation of sensing devices is also investigated using the numerical model. The results are suitable for the estimation of confidence range in practical measurements. Although the systematic error derived from this study can be use to calibrate the measured thermal conductivity, it is a function of the variable to be measured. Therefore to solve the problem, artificial neural networks (ANNs), which are trained using a variey of simulated measurement given by the numerical model, are used. A trained ANN can be used to predict directly the correct thermal conductivity without calibration using the measurement data. Finally, applying the results of accuracy analysis together with the correction of a prototype using the simplified hot plate method, a new device is designed and built with an accurate temperature control system and a well constructed ANN to promote the practical value of the measuring method.
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Ma, Clive, und 馬梓晏. „Steady-state solution of flow field, temperature field, and stress field in rapid thermal process“. Thesis, 2003. http://ndltd.ncl.edu.tw/handle/27820007890956411126.
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碩士國立臺灣科技大學
機械工程系
91
Rapid thermal processing (RTP) has been proven to be a core technology in manufacturing ULSI devices such as memory chips, logics and microprocessors. Due to the smaller thermal budget and shorter treating time, this single wafer processing can be widely used for annealing, cleaning, oxidation, chemical vapor deposition and nitridation. However, poor RTP system can lead to significant temperature difference in the wafer. The damage due to the presence of thermal stresses can limit the applicability of the rapid thermal processing. In this work the steady-state temperature and stress distribution and oxygen flow patterns in a rapid thermal processing system are investigated by using the finite-difference approach and a Simpson integration technique. The results show the thermal stress at the wafer will be decreased as the buoyancy effect, the double-heating side, low density of oxygen, low velocity of oxygen flow, or more chamber height was considered. Once the velocity is over 682.5 sccm, the wafer will be destroyed. For the oxygen flow patterns, it depends strongly on pressure and buoyancy effect. A shield is placed between the inlet and the wafer to protect the wafer from cooling directory, which is a good way to get better thermal uniformity at the wafer.
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Her, bing-shyan, und 何柄賢. „The study of inaccuracy of conventional one-dimensional parallel thermal resistance circuit model for steady two-dimensional steady state heat transfer problems of composite walls“. Thesis, 2005. http://ndltd.ncl.edu.tw/handle/48h7r3.
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碩士崑山科技大學
機械工程研究所
93
For the two-dimensional steady heat-transfer problems of composite walls without heat source, all the heat transfer textbooks and research papers have applied the one-dimensional Parallel Thermal Resistance Circuit (PTRC) model to analyze and solve those problems. Undoubtedly, applying the Series Thermal Resistance Circuit (STRC) model, whose essential characteristics are totally identical to Series Electrical Resistance Circuit (PERC), to solve the one-dimensional steady heat-transfer problems of composite walls is accurate. For the two-dimensional steady heat-transfer problems of composite walls, applying the PTRC model, whose essential characteristics are totally not identical to PERC model, to solve those problems is inaccurate. Thus, their solutions will generate big errors. This thesis proves that two-dimensional steady-state heat-transfer problems of composite walls should not be appropriately solved by the one-dimensional PTRC model. Because we found out that the interface temperatures (node points of PTRC) of the composite walls are not the same. It is a big different to the Parallel Electric Resistance Circuits (PERC) with the same voltage at the same node point. Thus, the conventional thinking of there is similarity between PTRC and PERC is absolutely wrong. In order to prove such theory, two typical composite wall examples are used to analyze by CFD software. We found that conventional one-dimensional PTRC model for two-dimensional steady-state heat-transfer problems of composite walls will generate very great errors by comparing with the numerical results. Additionally, the alternative one-dimensional Separately Series Thermal Resistance Circuit (SSTRC) model is developed in this study. From the errors generated by the SSTRC model, we can figure out under what conditions the SSTRC model can be suitable applied to solve the two-dimensional steady-state heat-transfer problems of composite walls.
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Marshallsay, P. G. (Patrick George). „A methodology for modelling the steady-state thermal performance of air conditioning systems / submitted by Patrick George Marshallsay“. 1996. http://hdl.handle.net/2440/18712.
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Single leaf in pocket on back end paper.Bibliography: p. 475-488.
xxviii, 488 p. : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
This study aims to develop a robust set of tools to model the performance of a range of composite coil configurations, to develop an operational model to predict the steady state performance of single and multizone air conditioning systems and to use the computational model as an exploratory tool to examine the performance of a series of candidate design solutions.
Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1996?
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Chang, Tso-Hung, und 張佐鴻. „Research on the influence of graphite layer to the steady state thermal resistance measurement method using infrared irradiation“. Thesis, 2014. http://ndltd.ncl.edu.tw/handle/87043844288829458864.
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碩士國立中央大學
光電科學與工程學系
102
Measurement of thermal resistance with infrared at steady state is a high adaptive and non-contact measuring method for thermal resistance. However, the graphite layer is convenient for measuring method, but it also brings out a problem that causes the temperature error on the heat source area. Therefore, in this research, finite element analysis (FEA) method is used to discuss temperature error from graphite layer. Accor- ding to definition of thermal resistance, finding the effective cross- sectional area along heat transfer propagation direction and using linear fitting to find a functional form which is used to calculate the highest temperature on the surface of sample. At last, performing experiment confirm simulation result.
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Hsu, Hung-Hsiao, und 許宏孝. „Three-Dimensional Steady-State Thermal Analyses of a High Voltage and High Frequency Transformer Using Finite Element Method“. Thesis, 2004. http://ndltd.ncl.edu.tw/handle/52781560764252187846.
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碩士逢甲大學
電機工程所
92
To design a reliable and economical high voltage and high frequency transformer, it is necessary to be able to predict accurately the temperature distribution within the transformer. For thermal analysis, this thesis presents a model for the transformer. Then, the three-dimensional finite element method is conducted to analyze. Due to the complicated physical geometry of the transformer, such as the anisotropic nature of the iron, low and high voltage windings, insulation layers and insulation oil, a two-dimensional thermal model can not describe the problem accurately. Hence, a three-dimensional thermal model is employed for this analysis. To reduce the simulation time, the equivalent thermal conductivities for low and high voltage windings are derived based on the choice of proper size of three-dimensional tetrahedral elements. Reasonable results are obtained.
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(5930123), Gaurav Patankar. „CHARACTERIZATION, MODELING AND DESIGN OF ULTRA-THIN VAPOR CHAMBER HEAT SPREADERS UNDER STEADY-STATE AND TRANSIENT CONDITIONS“. Thesis, 2019.
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This dissertation is focused on studying transport behavior in vapor chambers at ultra-thin form factors so that their use as heat spreaders can be extended to applications with extreme space constraints. Both the steady-state and transient thermal transport behaviors of vapor chambers are studied. The steady-state section presents an experimental characterization technique, methodologies for the design of the vapor chamber wick structure, and a working fluid selection procedure. The transient section develops a low-cost, 3D, transient semi-analytical transport model, which is used to explore the transient thermal behavior of thin vapor chambers: 1) The key mechanisms governing the transient behavior are identified and experimentally validated; 2) the transient performance of a vapor chamber relative to a copper heat spreader of the same external dimensions is explored and key performance thresholds are identified; and 3) practices are developed for the design of vapor chambers under transient conditions. These analyses have been tailored to ultra-thin vapor chamber geometries, focusing on the application of heat spreading in mobile electronic devices. Compared to the conventional scenarios of use for vapor chambers, this application is uniquely characterized by compact spaces, low and transient heat input, and heat rejection via natural convection.
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Kapoor, Divyansh. „QUANTIFICATION OF THERMAL BRIDGING EFFECTS IN COLD-FORMED STEEL WALL ASSEMBLIES“. 2020. https://scholarworks.umass.edu/masters_theses_2/880.
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Thermal bridging can be defined as the phenomenon where a structural element spanning the building envelope acts like a thermal pathway which collects and moves energy (heat) from the interior to the exterior of the structure. CFS construction, due to the high thermal conductivity of steel with respect to its surrounding structural components and repetitive nature of framing, is highly prone to thermal bridging. Thermal bridging significantly alters the thermal performance of wall assemblies.
Hence, the objective of this research project was to quantify the magnitude of energy loss through cold-formed steel (CFS) stud wall assemblies at a component level to lay the groundwork for future works that promote sustainable, energy-efficient, and improved building design recommendations.
Therefore, a parametric evaluation was performed using ISO 10211:2007, Annex A, conforming heat transfer software Blocon Heat3 version 8 to generate the data required for analysis. 80 unique wall assemblies and the impact of selected parameters on the overall thermal transmittance of the wall assembly were studied as part of the parametric evaluation. The key variables of the study are steel thickness, stud depth, stud spacing, cavity insulation R-value, external insulation thickness (R-value), and fastener diameter and length.
Based on the results of the analysis, effects of increasing stud and track thickness, depth, and stud spacing have been discussed in the form of trends in overall heat flow and linear thermal transmittance coefficient values. Additionaly, effects of increasing external insulation have been discussed by addressing changes in heat flow.
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Capelas, Stéphanie dos Santos. „Implementação de um modelo para simular o comportamento térmico de coberturas instaladas em câmara climática“. Master's thesis, 2017. http://hdl.handle.net/10316/83154.
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Dissertação de Mestrado Integrado em Engenharia do Ambiente apresentada à Faculdade de Ciências e TecnologiaO uso elevado de energia por parte dos edifícios surge como um dos problemas mais relevantes dos últimos tempos, surgindo a necessidade do estudo do comportamento térmico dos edifícios que depende muito das soluções que compõem a sua envolvente.A cobertura é um dos elementos do edifício com maiores flutuações térmicas. O isolamento térmico é um dos componentes com maior impacto na redução destas flutuações, sendo de elevada importância conhecer a sua natureza e as suas propriedades. Estes materiais são relevantes pela resistência térmica que oferecem, mas também pelo seu comportamento quando sujeitos a um regime transiente, já que contribuem significativamente no atraso térmico.Um exemplo de uma solução que pode apresentar um comportamento térmico bastante dinâmico é a cobertura verde porque além das propriedades dos materiais que a compõem têm o efeito do substrato e da vegetação. O comportamento destas camadas depende de diversos fatores, nomeadamente do teor de humidade, da densidade da vegetação, etc. O desenvolvimento e estudo deste tipo de soluções deve ser, por isso, alvo de investigação.A motivação do presente trabalho prende-se com avaliação do uso de aglomerado de cortiça expandida em soluções de coberturas verdes e da necessidade de implementar modelos que permitam a sua simulação em condições específicas de uso.No presente trabalho, a implementação e validação dos modelos de simulação foi realizada para os regimes permanente e transiente. Após a validação dos modelos através da comparação dos resultados obtidos nas simulações com as medições efetuadas numa campanha experimental efetua-se uma análise de três casos de estudo de modo a perceber as alterações ocorridas nas trocas de calor consoante os modelos se encontrem secos ou saturados, adicionando-se uma camada de substrato em dois casos de estudo, com propriedades diferentes.Os fluxos de calor ao longo do modelo com aglomerado de cortiça expandida aumenta cerca de 23%, quando saturado. Já os modelos com substrato têm fluxos de calor com um aumento entre os 30% e os 35%, quando saturados.
The high energy use by buildings reveals itself as one of the most relevant problems of recent times, arising the need to study the thermal behavior of buildings that depends a lot on the solutions considered for its surroundings.The roof is one of the elements of the building with greater thermal fluctuations. Thermal insulation is one of the components that has the greatest impact in reducing these fluctuations, and it is of great importance to know its nature and properties. These materials are relevant for the thermal resistance they present, but also for their behavior when subjected to a transient state, since they contribute significantly to the thermal delay.An example of a solution that can present a very dynamic thermal behavior is the green roof because in addition to the properties of the materials that compose it have the effect of the substrate and the vegetation. The behavior of these layers depends on several factors, namely the moisture content, the density of the vegetation, etc. The development and study of such solutions should therefore be the subject of research.The motivation of the present work is to evaluate the use of expanded cork agglomerates in green roofing solutions and the need to implement models that allow it´s simulation under specific conditions of use.In the present work, the implementation and validation of the simulation models was performed for the permanent and transient states. After the validation of the models through the comparison of the results obtained in the simulations with the measurements achieved by an experimental campaign. An analysis of three case studies is performed in order to perceive the changes occurred in the heat exchanges according to whether the models are dry or saturated, by adding a layer of substrate in two case studies with different properties.The heat fluxes along the model with expanded cork agglomerate increases about 23% when saturated. Already the substrate models have heat flows with an increase between 30% and 35% when saturated.
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Λυγκώνης, Ηλίας. „Θερμική ανάλυση ασύγχρονου κινητήρα στην μόνιμη κατάσταση λειτουργίας με την μέθοδο των συγκεντρωμένων παραμέτρων“. Thesis, 2012. http://hdl.handle.net/10889/5595.
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Η θερμική ανάλυση είναι μια σημαντική περιοχή μελέτης και γίνεται περισσότερο σημαντική για την σχεδίαση ηλεκτρικών μηχανών εξαιτίας της ανάγκης για μείωση του όγκου των υλικών και του κόστους κατασκευής τους καθώς και για την αύξηση της απόδοσής τους. Είναι εξίσου σημαντική με την ηλεκτρομαγνητική ανάλυση μιας και η θέρμανση της μηχανής θα οριοθετήσει την ονομαστική της ισχύ καθώς και την διάρκεια ζωής της μόνωσης. Στόχος της παρούσας διπλωματικής εργασίας είναι η εύρεση της κατανομής της θερμοκρασίας στο εσωτερικό ενός ασύγχρονου τριφασικού κινητήρα στη μόνιμη κατάσταση λειτουργίας του με τη μέθοδο των συγκεντρωμένων παραμέτρων.
Στο πρώτο κεφάλαιο αναφέρονται βασικές έννοιες της θερμοδυναμικής. Γίνεται αναφορά σε διάφορους συντελεστές, παρουσιάζονται οι θερμοδυναμικοί νόμοι και γίνεται σύντομη αναφορά στους μηχανισμούς μετάδοσης θερμότητας.
Στο δεύτερο κεφάλαιο δίνεται η αναλυτική περιγραφή των μηχανισμών μετάδοσης θερμότητας και παρουσιάζεται ένα απλό δίκτυο μοντελοποίησης με ισοδύναμες θερμικές αντιστάσεις.
Στο τρίτο κεφάλαιο παρουσιάζεται σύντομα η δομή, η αρχή λειτουργίας και οι τύποι μιας ασύγχρονης μηχανής. Εδώ επίσης αναφέρονται και οι διάφορες μορφές απωλειών ενέργειας κατά την λειτουργία μιας τριφασικής ασύγχρονης μηχανής. Παρουσιάζεται ακόμη ο υπό μελέτη κινητήρας και αναφέρονται τα θερμοστοιχεία που χρησιμοποιούνται στην πειραματική διαδικασία.
Στο τέταρτο κεφάλαιο περιγράφεται η μέθοδος θερμικής ανάλυσης με χρήση ισοδυνάμου κυκλώματος θερμικών αντιστάσεων για την μόνιμη κατάσταση. Στη συνέχεια δίνεται το προτεινόμενο κύκλωμα και παρουσιάζονται αναλυτικά οι ισοδύναμες θερμικές αντιστάσεις του μοντέλου.
Τέλος στο πέμπτο κεφάλαιο παρατίθενται τα αποτελέσματα της θερμικής ανάλυσης, γίνεται σύγκριση με τα πειραματικά δεδομένα θερμοκρασιακών τιμών που πάρθηκαν από τα θερμοστοιχεία και ακολουθεί η διαδικασία της παραμετροποίησης στους διάφορους συντελεστές που χρησιμοποιήθηκαν είτε υπολογίστηκαν κατά την ανάλυση.Thermal analysis is an important design area and becoming more important part of the electric motor design process due to the push for reduced weights and costs and increased efficiency. Thermal analysis is of equal importance as the electromagnetic design of the machine, because the temperature rise of the machine eventually determines the maximum output power. The purpose of this study is to record the temperature distribution of the internal parts of an induction motor at steady state using an equivalent thermal circuit with lumped parameters. The first chapter is an introduction of the thermodynamic theory. The laws of thermodynamics are described and there is a brief report of heat transfer mechanisms. The second chapter describes analytically the heat transfer mechanisms. Also, an example of modelling using thermal equivalent resistances is given. The third chapter introduces shortly the operational principles of an induction machine. Here are also referred the various losses that occur during the rotation of an induction motor. The studied induction motor, with the modified stator winding to include thermocouples, is shown. The fourth chapter introduces the method of thermal analysis using thermal equivalent circuit with lumped parameters. The proposed model is given and its components are described in particular. At last, in the fifth chapter the results of temperature distribution are given and compared with experimental data of temperature values that are acquired using the thermocouples. Here also takes apart the parameterising of the various coefficients that were used or calculated during this study.